Microstructure And Properties Of Ti-Zr-Nb Alloy Fabricated By Laser Additive Manufacturing

Laser additive manufacturing(LAM)is an advanced manufacturing technology developed on the basis of laser cladding technology and rapid prototyping technology.This technology inherits the advantages of laser cladding technology and rapid prototyping technology.It has many advantages,such as high flexibility,short cycle,low cost,integration of forming and microstructure performance control,etc.It provides a new way to prepare complex structural parts which are usually difficult to process.Therefore,in recent years,this technology has been widely concerned and valued in the world,and has made important progress in equipment development,software development,process and process control,etc.However,it is not commensurate with the fact that the basic research of LAM materials is still weak.The materials used are mainly based on traditional alloy systems,and the specificity of laser additive manufacturing process and microstrcture is not taken into consideration.As a result,there are very few laser materials that can be used in industry,which has become one of the bottlenecks restricting the wide application of this technology.Therefore,the development of alloy systems suitable for metal LAM is a necessary prerequisite and basis for the application and development of this technology.For this reason,a series of Ti-Zr-Nb alloys were designed on the basis of Ti-Zr congruentmelting alloy with good microstructure stability and formability,and Nb of β-Ti stabilizing element was used as alloying element.A series of Ti-Zr-Nb alloys which designed by "cluster + connecting atom" structural model were fabricated by LAM on pure titanium substrates.The mapping relationship between microstructure,mechanical properties,wear resistance,corrosion resistance and Nb content under non-equilibrium solidification conditions was systematically analyzed,and the intrinsic mechanism of cluster-based alloying was revealed.The experimental results show that the Ti-Zr-Nb alloys with different Nb content are composed of single-phase β-Ti solid solution under the condition of non-equilibrium solidification by LAM.However,the difference is that as the Nb content increases,the lattice constant of the β-Ti solid solution gradually increases.Under the action of multi-cycle,variable cycle and strong constrained remelting or micro-heat treatment of LAM,due to dynamic recovery and recrystallization,the internal microstructure of the formed body exhibits near equiaxed crystal growth morphology,while the final sedimentary layer has The typical directional growth dendritic morphology is characterized,and as the Nb content increases,the alloy solidification structure is uniformly refined.Influenced by the main controlling factor of liquid solidification zone,the surface roughness of the alloy increases slightly with the increase of Nb content,while the mechanical properties and friction and wear properties of the alloy increase gradually with the enhancement of solid solution strengthening and grain refinement.In addition,the corrosion resistance of Ti-Zr-Nb alloy is improved because the defect in the oxide film is reduced with the increase of Nb content.